The present invention relates to a seat belt system that is provided on a vehicle, for example, an automobile, for the purpose of protecting an occupant. More particularly, the present invention relates to a seat belt retractor designed so that a reel shaft for winding up a webbing is locked from rotating when an emergency situation occurs, thereby preventing the webbing from being pulled out.
A typical conventional seat belt retractor mounted on a vehicle, for example, an automobile, includes a reel shaft for winding up a webbing, a frame rotatably supporting both ends of the reel shaft, lock means disposed in between the frame and the reel shaft and arranged to allow rotation of the reel shaft under normal circumstances and to be activated, when need arises, so as to prevent rotation of the reel shaft in at least a direction in which the webbing is unwound, deceleration sensing means operating when deceleration exceeding a predetermined value acts on the vehicle, and means for activating the lock means in response to the operation of the deceleration sensing means, as disclosed, for example, in the specification and drawings of U.S. Pat. No. 4,796,918.
In such a seat belt retractor, the reel shaft is freely rotatable under normal circumstances. Therefore, the webbing can be unwound freely, and the occupant can move forwardly as desired. When an emergency situation occurs, e.g., when a high degree of deceleration acts on the vehicle, the deceleration sensing means operates on sensing the deceleration, causing the lock activating means to activate the lock means so as to lock the reel shaft from rotating. Consequently, the webbing is prevented from being pulled out, and the occupant's body is restrained by the webbing. Thus, inertial forward movement of the occupant's body is prevented.
Incidentally, many of conventional seat belt retractors of the type described above are provided with a webbing guide that guides the webbing when wound up and unwound. In the prior art, the webbing guide is rigidly provided, extending between the left and right side walls of the frame.
However, the webbing guide, which is rigidly secured to the left and right side walls of the frame, involves the problem that since the position of the webbing guide is fixed at all times, the guide angle of the webbing with respect to the webbing guide undesirably changes as the webbing take-up position changes in accordance with the roll diameter of webbing taken up on the reel shaft. If the webbing guide angle changes in this way, the webbing cannot smoothly be guided by the webbing guide. In addition, the webbing may be rubbed against the webbing guide.